1. Field of the Invention
The present invention relates generally to automotive vehicle bodies, and more particularly, to an assembly system for welding automotive vehicle bodies.
2. Description of Related Art
Currently, there exists assembly systems for welding together automotive vehicle bodies by programmable robots which provide respot or finish welding at successive welding stations. Examples of such an assembly system are disclosed in U.S. Pat. Nos. 4,162,387 and 4,256,947 by inventor De Candia. These assembly systems typically include a plurality of holding carrier pallets, each provided with locator pins, upon which the lower surface of a preassembled "body in white", composed of provisionally connected stamped sheet metal elements, rests. The pallets include clamping devices to clamp this preassembled body in white on the pallet in a predetermined position. A carrier supports the pallets and transfers the pallets along a route passing through one or more "framing" welding stations. Each framing welding station includes a programmable robot to perform the welding and interchangeable holding side frames hereafter called "side gates" able to engage a preassembled body in white supported by the pallet.
One disadvantage of the above patented assembly systems is that the body in white resting on the locator pins has to be located relative to the pallet which, in turn, has to be located relative to the carrier. As a result, the locator pins are located indirectly through the pallet. Since the dimensional accuracy of the pallets may vary, the accuracy in the reference location of the body in white may vary. This may affect welding quality and repeatability. Another disadvantage is that all pallets must all be dimensionally the same to control the accuracy of locating the body in white. This results in a large cost in fabricating the pallets. Yet another disadvantage is that the operational equipment used to transfer and locate the pallet must be maintained in good condition. Otherwise, the accuracy in locating the pallet may vary.